The present study was aimed to evaluate the speech behaviors of normal young adults under DAF condition with an audiofilter. The feedback speech was distorted with a lowpass and a high-pass filter. The subjects were 21 young adults, 18 males and 13 females. Each subject read 100-word passages under DAF (delay time 200 msec) with all-pass filtering, low-pass filtering above 1, 200, 1, 700 and 2, 400Hz, and high-pass filtering below 1, 200, 1, 700 and 2, 400Hz. The feedback level was 65dB above each hearing threshold, and the sound was delivered to both ears. The speech behaviors were analysed with reference to reading time ratio and articulatory error, comparing with those under normal auditory feedback (NAF). The results were as follows: 1. The speech behaviors were mostly disturbed under all-pass filtering. 2. The speech behaviors under low-pass filtering were more disturbed than those under highpass filtering. 3. There were little differences among speech behaviors under three conditions of filtering; 1, 200, 1, 700 and 2, 400Hz for low-pass and high-pass respectively. 4. In general, the DAF effects on the male were greater than the female. 5. It was concluded that the low frequency range of speech sound was mostly responsible for DAF effect.
This was to explore a method of hearing test for infants in a “free field” with the use of two speakers and observation of the auditory behavioural responses. The normal threshold of hearing and auditory behavioural responses of 270 normal infants, 30 in each of 1, 3, 5, 7, 9, 12, 18, 21, and 24 months old were obtained. By this method, the auditory behavioural responses of premature infants and low birthweight infants were measured to detect hearing loss in both groups and to find the possible causes of the hearing loss. It has been said that one of the major complications of nursing of premature infants is caused by the problem related to oxygen therapy. However, in this study there appeared no correlation between the duration of the incubation of infants and their hearing loss. There was a higher incidence of hearing loss in the low birthweight infants than in the premature infants, and moreover severe hearing loss was found among the low birthweight infants. From these findings the author concluded that physical underdevelopment of hearing organ was a factor of hearing loss.
A developmental test of auditory function was devised in terms of developmental neurology to aid in the early detection and assessment of hearing impairment in infants. The data used for the development of the test were collected from one hundred and ninty-four normal-hearing infants ranging from birth to fifteen months of age. The purpose of the test is to evaluate development of auditory function in infants involving detection, discrimination, recognition and comprehension of sounds and speech by using a scale of auditory responses. The scale consists of fourtyfive check items placed on a developmental continuum. The testing procedure is very simple: mothers are asked to check auditory responses of their own infant at home using the scale prior to audiological and otological examinations. Auditory tests including the developmental test of auditory function, behavioral observation audiometry and brainstem evoked response audiometry were performed on approximately fifty infants who needed audiological examination because of poverty of auditory response to enviromental sounds and human voices. The developmental test of auditory function was also applied to the auditory screening of 1173 infants who visited a health center in Tokyo to undergo health examinations during a period from February 1976 to July 1977. The results obtained indicated that combinations of the three differeent kinds of auditory tests such as behavioral, electrophysiological and developmental tests are the most adequate way of assessing auditory abilities in infants. The developmental test of auditory function can be a simple and useful means for the early detection and assessment of hearing impairment.